The present invention relates to moveable core guidewires, and more particularly relates to guidewires having safety wires therein.
In medical procedures such as angiography, catheters must be positioned deep in the vascular system, and often such catheters must reach difficult to access regions. In order to introduce such a catheter into the vascular system of a patient, a sharp cannula is inserted through the skin and into the vascular system, and then a spring guide wire is inserted through the cannula and advanced in the vascular system until its distal end reaches the location where the catheter tip is desired. The cannula is then removed from the patient's body and the catheter is inserted into the body by sliding over the guidewire. The guidewire generally then is withdrawn, and the catheter is ready for use. Catheters are also used in non-vascular procedures such as urinary tract procedures, and are introduced as described above, with the aid of the catheter guidewire.
As used herein, the terms "catheter" and "guidewire" are meant to encompass all types of catheters and guidewires. For convenience, however, the specific examples discussed herein relate to procedures dealing with the vascular system. Nevertheless, the present invention is not limited to catheters and guidewires designed for the vascular system, and the benefits and advantages of the present invention apply equally to any medical procedure where a catheter must be introduced through the skin and reach a remote location in the human body.
The specific type of guidewire forming the present invention is the moveable core guidewire. This type of guidewire generally is more flexible and steerable than the fixed core guidewire, and hence can be used in the more difficult to reach locations of the body.
The core wire of the moveable guidewire assembly provides a degree of strength, rigidity, and steerability such that the entire assembly can negotiate the vascular system. And it is known that the flexibility of the guidewire assembly can be altered by changing the flexibility of the core wire along the length thereof. Furthermore, with the moveable core guidewire, the flexibility of the guidewire assembly at the tip can be altered by moving the core wire into and out of the guidewire's distal end.
Structural integrity is another requisite for a successful guidewire. A broken guidewire, with the possibility of leaving debris in the patient's body, cannot be tolerated. A commonly employed precaution against leaving a broken guidewire tip in the vascular system of a patient, is the provision of a thin wire, termed a safety wire, inside the wound outer guidewire casing. The safety wire is customarily connected both to the proximate and distal ends of the guidewire to enable the removal of any broken fragments should a break occur in the outer spring of the guidewire assembly.
Some guidewire assemblies use a safety wire having a circular cross section, while others use a safety wire having a rectangular cross section. In both types of guidewire assemblies, the mere presence of the safety wire makes movement of the core wire more difficult.
Ideally, the safety wire should occupy the least amount of area in the guidewire assembly, for the more room the core wire has inside the guidewire assembly, the easier it is to manipulate the core wire by the medical personnel. Yet, in all the known prior art moveable core guidewires, the safety wire produces dead space, or wasted space, that cannot be used by the moveable core wire.
The moveable core guidewire assembly of the present invention utilizes a safety wire that overcomes the above drawback.